* [PATCH] softirq: Prevent looping on disabled tasklets
@ 2017-02-12 14:00 ` Chris Wilson
0 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 14:00 UTC (permalink / raw)
To: linux-kernel
Cc: intel-gfx, Chris Wilson, Tvrtko Ursulin, Thomas Gleixner,
Hannes Reinecke, Jens Axboe, Bjorn Helgaas, Alexander Potapenko,
Chen Fan, Ingo Molnar, Peter Zijlstra (Intel),
Sebastian Andrzej Siewior, Johannes Thumshirn, Emese Revfy,
Sagi Grimberg, Eric Dumazet, Tom Herbert, Ben Hutchings
Disabling a tasklet causes it not to run during tasklet_action, but is
put back onto the runnable tasklet list, and a new softirq raised. As
the softirq is raised from within __do_softirq() this causing
__do_softirq() to loop constantly until its timeslice expires and is
transferred to the ksoftirq thread. ksoftirq then permanently spins,
as on each action, the disabled tasklet keeps reraising the softirq.
Break this vicious cycle by moving the softirq from the action to the
final tasklet_enable().
This behaviour appears to be historic (since the first git import).
However, the looping until timeslice duration (to a max of 2ms) was
first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
with the restart limit restored in commit 34376a50fb1f ("Fix lockup
related to stop_machine being stuck in __do_softirq.")
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
---
include/linux/interrupt.h | 7 +++++--
kernel/softirq.c | 2 --
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 53144e78a369..12750f00d00d 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -613,8 +613,11 @@ static inline void tasklet_disable(struct tasklet_struct *t)
static inline void tasklet_enable(struct tasklet_struct *t)
{
- smp_mb__before_atomic();
- atomic_dec(&t->count);
+ if (!atomic_dec_and_test(&t->count))
+ return;
+
+ if (test_bit(TASKLET_STATE_SCHED, &t->state))
+ raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
}
extern void tasklet_kill(struct tasklet_struct *t);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 744fa611cae0..5a359eb1a541 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -527,7 +527,6 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_vec.tail) = t;
__this_cpu_write(tasklet_vec.tail, &(t->next));
- __raise_softirq_irqoff(TASKLET_SOFTIRQ);
local_irq_enable();
}
}
@@ -563,7 +562,6 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_hi_vec.tail) = t;
__this_cpu_write(tasklet_hi_vec.tail, &(t->next));
- __raise_softirq_irqoff(HI_SOFTIRQ);
local_irq_enable();
}
}
--
2.11.0
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH] softirq: Prevent looping on disabled tasklets
@ 2017-02-12 14:00 ` Chris Wilson
0 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 14:00 UTC (permalink / raw)
To: linux-kernel
Cc: Jens Axboe, Hannes Reinecke, Sagi Grimberg,
Peter Zijlstra (Intel),
intel-gfx, Chen Fan, Eric Dumazet, Emese Revfy,
Alexander Potapenko, Johannes Thumshirn, Bjorn Helgaas,
Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
Disabling a tasklet causes it not to run during tasklet_action, but is
put back onto the runnable tasklet list, and a new softirq raised. As
the softirq is raised from within __do_softirq() this causing
__do_softirq() to loop constantly until its timeslice expires and is
transferred to the ksoftirq thread. ksoftirq then permanently spins,
as on each action, the disabled tasklet keeps reraising the softirq.
Break this vicious cycle by moving the softirq from the action to the
final tasklet_enable().
This behaviour appears to be historic (since the first git import).
However, the looping until timeslice duration (to a max of 2ms) was
first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
with the restart limit restored in commit 34376a50fb1f ("Fix lockup
related to stop_machine being stuck in __do_softirq.")
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
---
include/linux/interrupt.h | 7 +++++--
kernel/softirq.c | 2 --
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 53144e78a369..12750f00d00d 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -613,8 +613,11 @@ static inline void tasklet_disable(struct tasklet_struct *t)
static inline void tasklet_enable(struct tasklet_struct *t)
{
- smp_mb__before_atomic();
- atomic_dec(&t->count);
+ if (!atomic_dec_and_test(&t->count))
+ return;
+
+ if (test_bit(TASKLET_STATE_SCHED, &t->state))
+ raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
}
extern void tasklet_kill(struct tasklet_struct *t);
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 744fa611cae0..5a359eb1a541 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -527,7 +527,6 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_vec.tail) = t;
__this_cpu_write(tasklet_vec.tail, &(t->next));
- __raise_softirq_irqoff(TASKLET_SOFTIRQ);
local_irq_enable();
}
}
@@ -563,7 +562,6 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_hi_vec.tail) = t;
__this_cpu_write(tasklet_hi_vec.tail, &(t->next));
- __raise_softirq_irqoff(HI_SOFTIRQ);
local_irq_enable();
}
}
--
2.11.0
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply related [flat|nested] 17+ messages in thread
* Re: [PATCH] softirq: Prevent looping on disabled tasklets
2017-02-12 14:00 ` Chris Wilson
@ 2017-02-12 14:23 ` Chris Wilson
-1 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 14:23 UTC (permalink / raw)
To: linux-kernel
Cc: intel-gfx, Tvrtko Ursulin, Thomas Gleixner, Hannes Reinecke,
Jens Axboe, Bjorn Helgaas, Alexander Potapenko, Chen Fan,
Ingo Molnar, Peter Zijlstra (Intel),
Sebastian Andrzej Siewior, Johannes Thumshirn, Emese Revfy,
Sagi Grimberg, Eric Dumazet, Tom Herbert, Ben Hutchings
On Sun, Feb 12, 2017 at 02:00:19PM +0000, Chris Wilson wrote:
> Disabling a tasklet causes it not to run during tasklet_action, but is
> put back onto the runnable tasklet list, and a new softirq raised. As
> the softirq is raised from within __do_softirq() this causing
> __do_softirq() to loop constantly until its timeslice expires and is
> transferred to the ksoftirq thread. ksoftirq then permanently spins,
> as on each action, the disabled tasklet keeps reraising the softirq.
>
> Break this vicious cycle by moving the softirq from the action to the
> final tasklet_enable().
>
> This behaviour appears to be historic (since the first git import).
> However, the looping until timeslice duration (to a max of 2ms) was
> first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
> with the restart limit restored in commit 34376a50fb1f ("Fix lockup
> related to stop_machine being stuck in __do_softirq.")
>
> Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Johannes Thumshirn <jthumshirn@suse.de>
> Cc: Emese Revfy <re.emese@gmail.com>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Tom Herbert <therbert@google.com>
> Cc: Ben Hutchings <bhutchings@solarflare.com>
> ---
> include/linux/interrupt.h | 7 +++++--
> kernel/softirq.c | 2 --
> 2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index 53144e78a369..12750f00d00d 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -613,8 +613,11 @@ static inline void tasklet_disable(struct tasklet_struct *t)
>
> static inline void tasklet_enable(struct tasklet_struct *t)
> {
> - smp_mb__before_atomic();
> - atomic_dec(&t->count);
> + if (!atomic_dec_and_test(&t->count))
> + return;
> +
> + if (test_bit(TASKLET_STATE_SCHED, &t->state))
> + raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
raise_softirq is not exported, so let's move tasklet_enable()
out-of-line and export that.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH] softirq: Prevent looping on disabled tasklets
@ 2017-02-12 14:23 ` Chris Wilson
0 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 14:23 UTC (permalink / raw)
To: linux-kernel
Cc: Jens Axboe, Hannes Reinecke, Sagi Grimberg,
Peter Zijlstra (Intel),
intel-gfx, Chen Fan, Eric Dumazet, Emese Revfy,
Alexander Potapenko, Johannes Thumshirn, Bjorn Helgaas,
Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
On Sun, Feb 12, 2017 at 02:00:19PM +0000, Chris Wilson wrote:
> Disabling a tasklet causes it not to run during tasklet_action, but is
> put back onto the runnable tasklet list, and a new softirq raised. As
> the softirq is raised from within __do_softirq() this causing
> __do_softirq() to loop constantly until its timeslice expires and is
> transferred to the ksoftirq thread. ksoftirq then permanently spins,
> as on each action, the disabled tasklet keeps reraising the softirq.
>
> Break this vicious cycle by moving the softirq from the action to the
> final tasklet_enable().
>
> This behaviour appears to be historic (since the first git import).
> However, the looping until timeslice duration (to a max of 2ms) was
> first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
> with the restart limit restored in commit 34376a50fb1f ("Fix lockup
> related to stop_machine being stuck in __do_softirq.")
>
> Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Johannes Thumshirn <jthumshirn@suse.de>
> Cc: Emese Revfy <re.emese@gmail.com>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Tom Herbert <therbert@google.com>
> Cc: Ben Hutchings <bhutchings@solarflare.com>
> ---
> include/linux/interrupt.h | 7 +++++--
> kernel/softirq.c | 2 --
> 2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index 53144e78a369..12750f00d00d 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -613,8 +613,11 @@ static inline void tasklet_disable(struct tasklet_struct *t)
>
> static inline void tasklet_enable(struct tasklet_struct *t)
> {
> - smp_mb__before_atomic();
> - atomic_dec(&t->count);
> + if (!atomic_dec_and_test(&t->count))
> + return;
> +
> + if (test_bit(TASKLET_STATE_SCHED, &t->state))
> + raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
raise_softirq is not exported, so let's move tasklet_enable()
out-of-line and export that.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 17+ messages in thread
* [PATCH v2] softirq: Prevent looping on disabled tasklets
2017-02-12 14:00 ` Chris Wilson
@ 2017-02-12 14:31 ` Chris Wilson
-1 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 14:31 UTC (permalink / raw)
To: linux-kernel
Cc: intel-gfx, Chris Wilson, Tvrtko Ursulin, Thomas Gleixner,
Hannes Reinecke, Jens Axboe, Bjorn Helgaas, Alexander Potapenko,
Chen Fan, Ingo Molnar, Peter Zijlstra (Intel),
Sebastian Andrzej Siewior, Johannes Thumshirn, Emese Revfy,
Sagi Grimberg, Eric Dumazet, Tom Herbert, Ben Hutchings
Disabling a tasklet causes it not to run during tasklet_action, but is
put back onto the runnable tasklet list, and a new softirq raised. As
the softirq is raised from within __do_softirq() this causing
__do_softirq() to loop constantly until its timeslice expires and is
transferred to the ksoftirq thread. ksoftirq then permanently spins,
as on each action, the disabled tasklet keeps reraising the softirq.
Break this vicious cycle by moving the softirq from the action to the
final tasklet_enable().
This behaviour appears to be historic (since the first git import).
However, the looping until timeslice duration (to a max of 2ms) was
first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
with the restart limit restored in commit 34376a50fb1f ("Fix lockup
related to stop_machine being stuck in __do_softirq.")
v2: Export tasklet_enable() to work with modules.
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
---
include/linux/interrupt.h | 7 +------
kernel/softirq.c | 12 ++++++++++--
2 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 53144e78a369..a1fa88e7e509 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -611,12 +611,7 @@ static inline void tasklet_disable(struct tasklet_struct *t)
smp_mb();
}
-static inline void tasklet_enable(struct tasklet_struct *t)
-{
- smp_mb__before_atomic();
- atomic_dec(&t->count);
-}
-
+extern void tasklet_enable(struct tasklet_struct *t);
extern void tasklet_kill(struct tasklet_struct *t);
extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
extern void tasklet_init(struct tasklet_struct *t,
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 080eb57789c4..ab8d9aeccb46 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -535,7 +535,6 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_vec.tail) = t;
__this_cpu_write(tasklet_vec.tail, &(t->next));
- __raise_softirq_irqoff(TASKLET_SOFTIRQ);
local_irq_enable();
}
}
@@ -571,7 +570,6 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_hi_vec.tail) = t;
__this_cpu_write(tasklet_hi_vec.tail, &(t->next));
- __raise_softirq_irqoff(HI_SOFTIRQ);
local_irq_enable();
}
}
@@ -587,6 +585,16 @@ void tasklet_init(struct tasklet_struct *t,
}
EXPORT_SYMBOL(tasklet_init);
+void tasklet_enable(struct tasklet_struct *t)
+{
+ if (!atomic_dec_and_test(&t->count))
+ return;
+
+ if (test_bit(TASKLET_STATE_SCHED, &t->state))
+ raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
+}
+EXPORT_SYMBOL(tasklet_enable);
+
void tasklet_kill(struct tasklet_struct *t)
{
if (in_interrupt())
--
2.11.0
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v2] softirq: Prevent looping on disabled tasklets
@ 2017-02-12 14:31 ` Chris Wilson
0 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 14:31 UTC (permalink / raw)
To: linux-kernel
Cc: Jens Axboe, Hannes Reinecke, Sagi Grimberg,
Peter Zijlstra (Intel),
intel-gfx, Chen Fan, Eric Dumazet, Emese Revfy,
Alexander Potapenko, Johannes Thumshirn, Bjorn Helgaas,
Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
Disabling a tasklet causes it not to run during tasklet_action, but is
put back onto the runnable tasklet list, and a new softirq raised. As
the softirq is raised from within __do_softirq() this causing
__do_softirq() to loop constantly until its timeslice expires and is
transferred to the ksoftirq thread. ksoftirq then permanently spins,
as on each action, the disabled tasklet keeps reraising the softirq.
Break this vicious cycle by moving the softirq from the action to the
final tasklet_enable().
This behaviour appears to be historic (since the first git import).
However, the looping until timeslice duration (to a max of 2ms) was
first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
with the restart limit restored in commit 34376a50fb1f ("Fix lockup
related to stop_machine being stuck in __do_softirq.")
v2: Export tasklet_enable() to work with modules.
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
---
include/linux/interrupt.h | 7 +------
kernel/softirq.c | 12 ++++++++++--
2 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 53144e78a369..a1fa88e7e509 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -611,12 +611,7 @@ static inline void tasklet_disable(struct tasklet_struct *t)
smp_mb();
}
-static inline void tasklet_enable(struct tasklet_struct *t)
-{
- smp_mb__before_atomic();
- atomic_dec(&t->count);
-}
-
+extern void tasklet_enable(struct tasklet_struct *t);
extern void tasklet_kill(struct tasklet_struct *t);
extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
extern void tasklet_init(struct tasklet_struct *t,
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 080eb57789c4..ab8d9aeccb46 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -535,7 +535,6 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_vec.tail) = t;
__this_cpu_write(tasklet_vec.tail, &(t->next));
- __raise_softirq_irqoff(TASKLET_SOFTIRQ);
local_irq_enable();
}
}
@@ -571,7 +570,6 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
t->next = NULL;
*__this_cpu_read(tasklet_hi_vec.tail) = t;
__this_cpu_write(tasklet_hi_vec.tail, &(t->next));
- __raise_softirq_irqoff(HI_SOFTIRQ);
local_irq_enable();
}
}
@@ -587,6 +585,16 @@ void tasklet_init(struct tasklet_struct *t,
}
EXPORT_SYMBOL(tasklet_init);
+void tasklet_enable(struct tasklet_struct *t)
+{
+ if (!atomic_dec_and_test(&t->count))
+ return;
+
+ if (test_bit(TASKLET_STATE_SCHED, &t->state))
+ raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
+}
+EXPORT_SYMBOL(tasklet_enable);
+
void tasklet_kill(struct tasklet_struct *t)
{
if (in_interrupt())
--
2.11.0
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply related [flat|nested] 17+ messages in thread
* ✗ Fi.CI.BAT: failure for softirq: Prevent looping on disabled tasklets
2017-02-12 14:00 ` Chris Wilson
` (2 preceding siblings ...)
(?)
@ 2017-02-12 14:32 ` Patchwork
-1 siblings, 0 replies; 17+ messages in thread
From: Patchwork @ 2017-02-12 14:32 UTC (permalink / raw)
To: Chris Wilson; +Cc: intel-gfx
== Series Details ==
Series: softirq: Prevent looping on disabled tasklets
URL : https://patchwork.freedesktop.org/series/19515/
State : failure
== Summary ==
CHECK usr/include/linux/dvb/ (8 files)
CHECK usr/include/linux/android/ (1 files)
CHECK usr/include/linux/byteorder/ (2 files)
CHECK usr/include/linux/caif/ (2 files)
CHECK usr/include/linux/ (443 files)
CHECK usr/include/linux/netfilter_bridge/ (17 files)
CHECK usr/include/linux/spi/ (1 files)
CHECK usr/include/linux/iio/ (2 files)
CHECK usr/include/linux/netfilter_ipv4/ (9 files)
CHECK usr/include/linux/isdn/ (1 files)
CHECK usr/include/linux/hsi/ (2 files)
CHECK usr/include/linux/tc_ematch/ (4 files)
CHECK usr/include/linux/netfilter_arp/ (2 files)
CHECK usr/include/linux/hdlc/ (1 files)
CHECK usr/include/linux/wimax/ (1 files)
CHECK usr/include/linux/mmc/ (1 files)
CHECK usr/include/linux/usb/ (11 files)
CHECK usr/include/linux/can/ (5 files)
CHECK usr/include/linux/raid/ (2 files)
CHECK usr/include/linux/sunrpc/ (1 files)
CHECK usr/include/linux/netfilter/ (87 files)
CHECK usr/include/linux/netfilter_ipv6/ (12 files)
CHECK usr/include/linux/nfsd/ (5 files)
CHECK usr/include/linux/netfilter/ipset/ (4 files)
CHECK usr/include/linux/tc_act/ (14 files)
CHECK usr/include/asm/ (62 files)
GEN .version
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o
LD init/built-in.o
LD vmlinux.o
MODPOST vmlinux.o
KSYM .tmp_kallsyms1.o
KSYM .tmp_kallsyms2.o
LD vmlinux
SORTEX vmlinux
SYSMAP System.map
CC arch/x86/boot/a20.o
AS arch/x86/boot/bioscall.o
CC arch/x86/boot/cmdline.o
AS arch/x86/boot/copy.o
HOSTCC arch/x86/boot/mkcpustr
CC arch/x86/boot/cpuflags.o
CC arch/x86/boot/early_serial_console.o
CC arch/x86/boot/cpucheck.o
CC arch/x86/boot/main.o
CC arch/x86/boot/printf.o
CC arch/x86/boot/edd.o
CC arch/x86/boot/memory.o
CC arch/x86/boot/pm.o
CC arch/x86/boot/tty.o
AS arch/x86/boot/pmjump.o
CC arch/x86/boot/video.o
CC arch/x86/boot/video-mode.o
CC arch/x86/boot/version.o
CC arch/x86/boot/string.o
CC arch/x86/boot/video-vga.o
CC arch/x86/boot/video-vesa.o
CC arch/x86/boot/video-bios.o
CC arch/x86/boot/regs.o
HOSTCC arch/x86/boot/tools/build
Building modules, stage 2.
CPUSTR arch/x86/boot/cpustr.h
CC arch/x86/boot/cpu.o
MODPOST 99 modules
LDS arch/x86/boot/compressed/vmlinux.lds
AS arch/x86/boot/compressed/head_64.o
VOFFSET arch/x86/boot/compressed/../voffset.h
CC arch/x86/boot/compressed/string.o
CC arch/x86/boot/compressed/cmdline.o
HOSTCC arch/x86/boot/compressed/mkpiggy
CC arch/x86/boot/compressed/cpuflags.o
CC arch/x86/boot/compressed/early_serial_console.o
CC arch/x86/boot/compressed/eboot.o
AS arch/x86/boot/compressed/efi_stub_64.o
OBJCOPY arch/x86/boot/compressed/vmlinux.bin
CC arch/x86/boot/compressed/error.o
XZKERN arch/x86/boot/compressed/vmlinux.bin.xz
ERROR: "raise_softirq" [drivers/gpu/drm/i915/i915.ko] undefined!
scripts/Makefile.modpost:91: recipe for target '__modpost' failed
make[1]: *** [__modpost] Error 1
Makefile:1196: recipe for target 'modules' failed
make: *** [modules] Error 2
make: *** Waiting for unfinished jobs....
CC arch/x86/boot/compressed/misc.o
MKPIGGY arch/x86/boot/compressed/piggy.S
AS arch/x86/boot/compressed/piggy.o
DATAREL arch/x86/boot/compressed/vmlinux
LD arch/x86/boot/compressed/vmlinux
ZOFFSET arch/x86/boot/zoffset.h
OBJCOPY arch/x86/boot/vmlinux.bin
AS arch/x86/boot/header.o
LD arch/x86/boot/setup.elf
OBJCOPY arch/x86/boot/setup.bin
BUILD arch/x86/boot/bzImage
Setup is 16412 bytes (padded to 16896 bytes).
System is 4854 kB
CRC e2277ba4
Kernel: arch/x86/boot/bzImage is ready (#1)
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [Intel-gfx] [PATCH] softirq: Prevent looping on disabled tasklets
2017-02-12 14:00 ` Chris Wilson
` (3 preceding siblings ...)
(?)
@ 2017-02-12 15:04 ` kbuild test robot
-1 siblings, 0 replies; 17+ messages in thread
From: kbuild test robot @ 2017-02-12 15:04 UTC (permalink / raw)
To: Chris Wilson
Cc: kbuild-all, linux-kernel, Jens Axboe, Hannes Reinecke,
Sagi Grimberg, Peter Zijlstra (Intel),
intel-gfx, Chen Fan, Eric Dumazet, Emese Revfy,
Alexander Potapenko, Johannes Thumshirn, Bjorn Helgaas,
Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
[-- Attachment #1: Type: text/plain, Size: 772 bytes --]
Hi Chris,
[auto build test ERROR on linus/master]
[also build test ERROR on v4.10-rc7 next-20170210]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Chris-Wilson/softirq-Prevent-looping-on-disabled-tasklets/20170212-220435
config: x86_64-lkp (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
>> ERROR: "raise_softirq" [net/mac80211/mac80211.ko] undefined!
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 24664 bytes --]
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [Intel-gfx] [PATCH] softirq: Prevent looping on disabled tasklets
2017-02-12 14:00 ` Chris Wilson
@ 2017-02-12 15:16 ` kbuild test robot
-1 siblings, 0 replies; 17+ messages in thread
From: kbuild test robot @ 2017-02-12 15:16 UTC (permalink / raw)
To: Chris Wilson
Cc: kbuild-all, linux-kernel, Jens Axboe, Hannes Reinecke,
Sagi Grimberg, Peter Zijlstra (Intel),
intel-gfx, Chen Fan, Eric Dumazet, Emese Revfy,
Alexander Potapenko, Johannes Thumshirn, Bjorn Helgaas,
Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
[-- Attachment #1: Type: text/plain, Size: 1255 bytes --]
Hi Chris,
[auto build test ERROR on linus/master]
[also build test ERROR on v4.10-rc7 next-20170210]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Chris-Wilson/softirq-Prevent-looping-on-disabled-tasklets/20170212-220435
config: x86_64-rhel (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
>> ERROR: "raise_softirq" [sound/pci/asihpi/snd-asihpi.ko] undefined!
>> ERROR: "raise_softirq" [net/mac802154/mac802154.ko] undefined!
ERROR: "raise_softirq" [net/mac80211/mac80211.ko] undefined!
>> ERROR: "raise_softirq" [drivers/usb/atm/usbatm.ko] undefined!
>> ERROR: "raise_softirq" [drivers/net/ethernet/jme.ko] undefined!
>> ERROR: "raise_softirq" [drivers/media/pci/mantis/mantis_core.ko] undefined!
>> ERROR: "raise_softirq" [drivers/hv/hv_vmbus.ko] undefined!
>> ERROR: "raise_softirq" [drivers/firewire/firewire-ohci.ko] undefined!
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 38265 bytes --]
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH] softirq: Prevent looping on disabled tasklets
@ 2017-02-12 15:16 ` kbuild test robot
0 siblings, 0 replies; 17+ messages in thread
From: kbuild test robot @ 2017-02-12 15:16 UTC (permalink / raw)
To: Chris Wilson
Cc: Jens Axboe, Hannes Reinecke, Sagi Grimberg,
Peter Zijlstra (Intel),
intel-gfx, linux-kernel, Bjorn Helgaas, Eric Dumazet,
Emese Revfy, Alexander Potapenko, kbuild-all, Johannes Thumshirn,
Chen Fan, Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
[-- Attachment #1: Type: text/plain, Size: 1255 bytes --]
Hi Chris,
[auto build test ERROR on linus/master]
[also build test ERROR on v4.10-rc7 next-20170210]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Chris-Wilson/softirq-Prevent-looping-on-disabled-tasklets/20170212-220435
config: x86_64-rhel (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
>> ERROR: "raise_softirq" [sound/pci/asihpi/snd-asihpi.ko] undefined!
>> ERROR: "raise_softirq" [net/mac802154/mac802154.ko] undefined!
ERROR: "raise_softirq" [net/mac80211/mac80211.ko] undefined!
>> ERROR: "raise_softirq" [drivers/usb/atm/usbatm.ko] undefined!
>> ERROR: "raise_softirq" [drivers/net/ethernet/jme.ko] undefined!
>> ERROR: "raise_softirq" [drivers/media/pci/mantis/mantis_core.ko] undefined!
>> ERROR: "raise_softirq" [drivers/hv/hv_vmbus.ko] undefined!
>> ERROR: "raise_softirq" [drivers/firewire/firewire-ohci.ko] undefined!
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 38265 bytes --]
[-- Attachment #3: Type: text/plain, Size: 160 bytes --]
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 17+ messages in thread
* ✗ Fi.CI.BAT: failure for softirq: Prevent looping on disabled tasklets (rev2)
2017-02-12 14:00 ` Chris Wilson
` (5 preceding siblings ...)
(?)
@ 2017-02-12 15:22 ` Patchwork
-1 siblings, 0 replies; 17+ messages in thread
From: Patchwork @ 2017-02-12 15:22 UTC (permalink / raw)
To: Chris Wilson; +Cc: intel-gfx
== Series Details ==
Series: softirq: Prevent looping on disabled tasklets (rev2)
URL : https://patchwork.freedesktop.org/series/19515/
State : failure
== Summary ==
Series 19515v2 softirq: Prevent looping on disabled tasklets
https://patchwork.freedesktop.org/api/1.0/series/19515/revisions/2/mbox/
Test core_auth:
Subgroup basic-auth:
pass -> TIMEOUT (fi-skl-6700k)
Test core_prop_blob:
Subgroup basic:
pass -> INCOMPLETE (fi-skl-6700k)
Test gem_close_race:
Subgroup basic-process:
pass -> TIMEOUT (fi-skl-6700hq)
pass -> TIMEOUT (fi-skl-6770hq)
Subgroup basic-threads:
pass -> INCOMPLETE (fi-skl-6700hq)
pass -> TIMEOUT (fi-bxt-j4205)
pass -> INCOMPLETE (fi-skl-6770hq) FDO#99742
pass -> TIMEOUT (fi-bsw-n3050)
Test gem_cpu_reloc:
Subgroup basic:
pass -> INCOMPLETE (fi-bsw-n3050)
Test gem_ctx_switch:
Subgroup basic-default:
pass -> INCOMPLETE (fi-bxt-j4205)
pass -> TIMEOUT (fi-bdw-5557u)
pass -> TIMEOUT (fi-kbl-7500u)
Subgroup basic-default-heavy:
pass -> INCOMPLETE (fi-kbl-7500u)
Test gem_exec_flush:
Subgroup basic-batch-kernel-default-uc:
pass -> TIMEOUT (fi-skl-6260u)
pass -> INCOMPLETE (fi-bdw-5557u)
pass -> TIMEOUT (fi-bxt-t5700)
Subgroup basic-batch-kernel-default-wb:
pass -> INCOMPLETE (fi-bxt-t5700)
pass -> INCOMPLETE (fi-skl-6260u)
FDO#99742 https://bugs.freedesktop.org/show_bug.cgi?id=99742
fi-bdw-5557u total:51 pass:48 dwarn:0 dfail:0 fail:0 skip:1
fi-bsw-n3050 total:13 pass:11 dwarn:0 dfail:0 fail:0 skip:0
fi-bxt-j4205 total:21 pass:19 dwarn:0 dfail:0 fail:0 skip:0
fi-bxt-t5700 total:52 pass:43 dwarn:0 dfail:0 fail:0 skip:7
fi-byt-j1900 total:252 pass:225 dwarn:0 dfail:0 fail:0 skip:27
fi-byt-n2820 total:252 pass:221 dwarn:0 dfail:0 fail:0 skip:31
fi-hsw-4770 total:252 pass:236 dwarn:0 dfail:0 fail:0 skip:16
fi-hsw-4770r total:252 pass:236 dwarn:0 dfail:0 fail:0 skip:16
fi-ilk-650 total:252 pass:202 dwarn:0 dfail:0 fail:0 skip:50
fi-ivb-3520m total:252 pass:234 dwarn:0 dfail:0 fail:0 skip:18
fi-ivb-3770 total:252 pass:234 dwarn:0 dfail:0 fail:0 skip:18
fi-kbl-7500u total:22 pass:20 dwarn:0 dfail:0 fail:0 skip:0
fi-skl-6260u total:52 pass:49 dwarn:0 dfail:0 fail:0 skip:1
fi-skl-6700hq total:12 pass:10 dwarn:0 dfail:0 fail:0 skip:0
fi-skl-6700k total:2 pass:0 dwarn:0 dfail:0 fail:0 skip:0
fi-skl-6770hq total:12 pass:10 dwarn:0 dfail:0 fail:0 skip:0
fi-snb-2520m total:252 pass:224 dwarn:0 dfail:0 fail:0 skip:28
fi-snb-2600 total:252 pass:223 dwarn:0 dfail:0 fail:0 skip:29
f48164e93e75dbbe0bb9dac254779eeea08c0657 drm-tip: 2017y-02m-12d-11h-10m-28s UTC integration manifest
8a1a5d9 softirq: Prevent looping on disabled tasklets
== Logs ==
For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_3782/
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 17+ messages in thread
* [PATCH v3] softirq: Prevent looping on disabled tasklets
2017-02-12 14:00 ` Chris Wilson
@ 2017-02-12 15:46 ` Chris Wilson
-1 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 15:46 UTC (permalink / raw)
To: linux-kernel
Cc: intel-gfx, Chris Wilson, Tvrtko Ursulin, Thomas Gleixner,
Hannes Reinecke, Jens Axboe, Bjorn Helgaas, Alexander Potapenko,
Chen Fan, Ingo Molnar, Peter Zijlstra (Intel),
Sebastian Andrzej Siewior, Johannes Thumshirn, Emese Revfy,
Sagi Grimberg, Eric Dumazet, Tom Herbert, Ben Hutchings
Disabling a tasklet causes it not to run during tasklet_action, but is
put back onto the runnable tasklet list, and a new softirq raised. As
the softirq is raised from within __do_softirq() this causing
__do_softirq() to loop constantly until its timeslice expires and is
transferred to the ksoftirq thread. ksoftirq then permanently spins,
as on each action, the disabled tasklet keeps reraising the softirq.
Break this vicious cycle by moving the softirq from the action to the
final tasklet_enable().
This behaviour appears to be historic (since the first git import).
However, the looping until timeslice duration (to a max of 2ms) was
first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
with the restart limit restored in commit 34376a50fb1f ("Fix lockup
related to stop_machine being stuck in __do_softirq.")
v2: Export tasklet_enable() to work with modules.
v3: Restore the looping over a failed tasklet_trylock()
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
---
include/linux/interrupt.h | 7 +------
kernel/softirq.c | 20 ++++++++++++++++++--
2 files changed, 19 insertions(+), 8 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 53144e78a369..a1fa88e7e509 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -611,12 +611,7 @@ static inline void tasklet_disable(struct tasklet_struct *t)
smp_mb();
}
-static inline void tasklet_enable(struct tasklet_struct *t)
-{
- smp_mb__before_atomic();
- atomic_dec(&t->count);
-}
-
+extern void tasklet_enable(struct tasklet_struct *t);
extern void tasklet_kill(struct tasklet_struct *t);
extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
extern void tasklet_init(struct tasklet_struct *t,
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 080eb57789c4..47c8933d315e 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -516,6 +516,7 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
while (list) {
struct tasklet_struct *t = list;
+ bool raise_softirq = true;
list = list->next;
@@ -529,13 +530,15 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
continue;
}
tasklet_unlock(t);
+ raise_softirq = false;
}
local_irq_disable();
t->next = NULL;
*__this_cpu_read(tasklet_vec.tail) = t;
__this_cpu_write(tasklet_vec.tail, &(t->next));
- __raise_softirq_irqoff(TASKLET_SOFTIRQ);
+ if (raise_softirq)
+ __raise_softirq_irqoff(TASKLET_SOFTIRQ);
local_irq_enable();
}
}
@@ -552,6 +555,7 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
while (list) {
struct tasklet_struct *t = list;
+ bool raise_softirq = true;
list = list->next;
@@ -565,13 +569,15 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
continue;
}
tasklet_unlock(t);
+ raise_softirq = false;
}
local_irq_disable();
t->next = NULL;
*__this_cpu_read(tasklet_hi_vec.tail) = t;
__this_cpu_write(tasklet_hi_vec.tail, &(t->next));
- __raise_softirq_irqoff(HI_SOFTIRQ);
+ if (raise_softirq)
+ __raise_softirq_irqoff(HI_SOFTIRQ);
local_irq_enable();
}
}
@@ -587,6 +593,16 @@ void tasklet_init(struct tasklet_struct *t,
}
EXPORT_SYMBOL(tasklet_init);
+void tasklet_enable(struct tasklet_struct *t)
+{
+ if (!atomic_dec_and_test(&t->count))
+ return;
+
+ if (test_bit(TASKLET_STATE_SCHED, &t->state))
+ raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
+}
+EXPORT_SYMBOL(tasklet_enable);
+
void tasklet_kill(struct tasklet_struct *t)
{
if (in_interrupt())
--
2.11.0
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v3] softirq: Prevent looping on disabled tasklets
@ 2017-02-12 15:46 ` Chris Wilson
0 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 15:46 UTC (permalink / raw)
To: linux-kernel
Cc: Jens Axboe, Hannes Reinecke, Sagi Grimberg,
Peter Zijlstra (Intel),
intel-gfx, Chen Fan, Eric Dumazet, Emese Revfy,
Alexander Potapenko, Johannes Thumshirn, Bjorn Helgaas,
Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
Disabling a tasklet causes it not to run during tasklet_action, but is
put back onto the runnable tasklet list, and a new softirq raised. As
the softirq is raised from within __do_softirq() this causing
__do_softirq() to loop constantly until its timeslice expires and is
transferred to the ksoftirq thread. ksoftirq then permanently spins,
as on each action, the disabled tasklet keeps reraising the softirq.
Break this vicious cycle by moving the softirq from the action to the
final tasklet_enable().
This behaviour appears to be historic (since the first git import).
However, the looping until timeslice duration (to a max of 2ms) was
first introduced in commit c10d73671ad3 ("softirq: reduce latencies"),
with the restart limit restored in commit 34376a50fb1f ("Fix lockup
related to stop_machine being stuck in __do_softirq.")
v2: Export tasklet_enable() to work with modules.
v3: Restore the looping over a failed tasklet_trylock()
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
---
include/linux/interrupt.h | 7 +------
kernel/softirq.c | 20 ++++++++++++++++++--
2 files changed, 19 insertions(+), 8 deletions(-)
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 53144e78a369..a1fa88e7e509 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -611,12 +611,7 @@ static inline void tasklet_disable(struct tasklet_struct *t)
smp_mb();
}
-static inline void tasklet_enable(struct tasklet_struct *t)
-{
- smp_mb__before_atomic();
- atomic_dec(&t->count);
-}
-
+extern void tasklet_enable(struct tasklet_struct *t);
extern void tasklet_kill(struct tasklet_struct *t);
extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
extern void tasklet_init(struct tasklet_struct *t,
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 080eb57789c4..47c8933d315e 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -516,6 +516,7 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
while (list) {
struct tasklet_struct *t = list;
+ bool raise_softirq = true;
list = list->next;
@@ -529,13 +530,15 @@ static __latent_entropy void tasklet_action(struct softirq_action *a)
continue;
}
tasklet_unlock(t);
+ raise_softirq = false;
}
local_irq_disable();
t->next = NULL;
*__this_cpu_read(tasklet_vec.tail) = t;
__this_cpu_write(tasklet_vec.tail, &(t->next));
- __raise_softirq_irqoff(TASKLET_SOFTIRQ);
+ if (raise_softirq)
+ __raise_softirq_irqoff(TASKLET_SOFTIRQ);
local_irq_enable();
}
}
@@ -552,6 +555,7 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
while (list) {
struct tasklet_struct *t = list;
+ bool raise_softirq = true;
list = list->next;
@@ -565,13 +569,15 @@ static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
continue;
}
tasklet_unlock(t);
+ raise_softirq = false;
}
local_irq_disable();
t->next = NULL;
*__this_cpu_read(tasklet_hi_vec.tail) = t;
__this_cpu_write(tasklet_hi_vec.tail, &(t->next));
- __raise_softirq_irqoff(HI_SOFTIRQ);
+ if (raise_softirq)
+ __raise_softirq_irqoff(HI_SOFTIRQ);
local_irq_enable();
}
}
@@ -587,6 +593,16 @@ void tasklet_init(struct tasklet_struct *t,
}
EXPORT_SYMBOL(tasklet_init);
+void tasklet_enable(struct tasklet_struct *t)
+{
+ if (!atomic_dec_and_test(&t->count))
+ return;
+
+ if (test_bit(TASKLET_STATE_SCHED, &t->state))
+ raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
+}
+EXPORT_SYMBOL(tasklet_enable);
+
void tasklet_kill(struct tasklet_struct *t)
{
if (in_interrupt())
--
2.11.0
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https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply related [flat|nested] 17+ messages in thread
* Re: [PATCH v3] softirq: Prevent looping on disabled tasklets
2017-02-12 15:46 ` Chris Wilson
@ 2017-02-12 16:03 ` Chris Wilson
-1 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 16:03 UTC (permalink / raw)
To: linux-kernel
Cc: intel-gfx, Tvrtko Ursulin, Thomas Gleixner, Hannes Reinecke,
Jens Axboe, Bjorn Helgaas, Alexander Potapenko, Chen Fan,
Ingo Molnar, Peter Zijlstra (Intel),
Sebastian Andrzej Siewior, Johannes Thumshirn, Emese Revfy,
Sagi Grimberg, Eric Dumazet, Tom Herbert, Ben Hutchings
On Sun, Feb 12, 2017 at 03:46:09PM +0000, Chris Wilson wrote:
> +void tasklet_enable(struct tasklet_struct *t)
> +{
> + if (!atomic_dec_and_test(&t->count))
> + return;
> +
> + if (test_bit(TASKLET_STATE_SCHED, &t->state))
> + raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
And of course this can't work as raise_softirq() is local to the cpu.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v3] softirq: Prevent looping on disabled tasklets
@ 2017-02-12 16:03 ` Chris Wilson
0 siblings, 0 replies; 17+ messages in thread
From: Chris Wilson @ 2017-02-12 16:03 UTC (permalink / raw)
To: linux-kernel
Cc: Jens Axboe, Hannes Reinecke, Sagi Grimberg,
Peter Zijlstra (Intel),
intel-gfx, Chen Fan, Eric Dumazet, Emese Revfy,
Alexander Potapenko, Johannes Thumshirn, Bjorn Helgaas,
Ben Hutchings, Thomas Gleixner, Ingo Molnar,
Sebastian Andrzej Siewior, Tom Herbert
On Sun, Feb 12, 2017 at 03:46:09PM +0000, Chris Wilson wrote:
> +void tasklet_enable(struct tasklet_struct *t)
> +{
> + if (!atomic_dec_and_test(&t->count))
> + return;
> +
> + if (test_bit(TASKLET_STATE_SCHED, &t->state))
> + raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
And of course this can't work as raise_softirq() is local to the cpu.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
_______________________________________________
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Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 17+ messages in thread
* ✓ Fi.CI.BAT: success for softirq: Prevent looping on disabled tasklets (rev3)
2017-02-12 14:00 ` Chris Wilson
` (7 preceding siblings ...)
(?)
@ 2017-02-12 16:22 ` Patchwork
-1 siblings, 0 replies; 17+ messages in thread
From: Patchwork @ 2017-02-12 16:22 UTC (permalink / raw)
To: Chris Wilson; +Cc: intel-gfx
== Series Details ==
Series: softirq: Prevent looping on disabled tasklets (rev3)
URL : https://patchwork.freedesktop.org/series/19515/
State : success
== Summary ==
Series 19515v3 softirq: Prevent looping on disabled tasklets
https://patchwork.freedesktop.org/api/1.0/series/19515/revisions/3/mbox/
fi-bdw-5557u total:252 pass:241 dwarn:0 dfail:0 fail:0 skip:11
fi-bsw-n3050 total:252 pass:213 dwarn:0 dfail:0 fail:0 skip:39
fi-bxt-j4205 total:252 pass:233 dwarn:0 dfail:0 fail:0 skip:19
fi-bxt-t5700 total:83 pass:70 dwarn:0 dfail:0 fail:0 skip:12
fi-byt-j1900 total:252 pass:225 dwarn:0 dfail:0 fail:0 skip:27
fi-byt-n2820 total:252 pass:221 dwarn:0 dfail:0 fail:0 skip:31
fi-hsw-4770 total:252 pass:236 dwarn:0 dfail:0 fail:0 skip:16
fi-hsw-4770r total:252 pass:236 dwarn:0 dfail:0 fail:0 skip:16
fi-ilk-650 total:252 pass:202 dwarn:0 dfail:0 fail:0 skip:50
fi-ivb-3520m total:252 pass:234 dwarn:0 dfail:0 fail:0 skip:18
fi-ivb-3770 total:252 pass:234 dwarn:0 dfail:0 fail:0 skip:18
fi-kbl-7500u total:252 pass:234 dwarn:0 dfail:0 fail:0 skip:18
fi-skl-6260u total:252 pass:242 dwarn:0 dfail:0 fail:0 skip:10
fi-skl-6700hq total:252 pass:235 dwarn:0 dfail:0 fail:0 skip:17
fi-skl-6700k total:252 pass:230 dwarn:4 dfail:0 fail:0 skip:18
fi-skl-6770hq total:252 pass:242 dwarn:0 dfail:0 fail:0 skip:10
fi-snb-2520m total:252 pass:224 dwarn:0 dfail:0 fail:0 skip:28
fi-snb-2600 total:252 pass:223 dwarn:0 dfail:0 fail:0 skip:29
f48164e93e75dbbe0bb9dac254779eeea08c0657 drm-tip: 2017y-02m-12d-11h-10m-28s UTC integration manifest
1ffceb2 softirq: Prevent looping on disabled tasklets
== Logs ==
For more details see: https://intel-gfx-ci.01.org/CI/Patchwork_3783/
_______________________________________________
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https://lists.freedesktop.org/mailman/listinfo/intel-gfx
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v3] softirq: Prevent looping on disabled tasklets
2017-02-12 16:03 ` Chris Wilson
(?)
@ 2017-02-17 11:55 ` Thomas Gleixner
-1 siblings, 0 replies; 17+ messages in thread
From: Thomas Gleixner @ 2017-02-17 11:55 UTC (permalink / raw)
To: Chris Wilson
Cc: linux-kernel, intel-gfx, Tvrtko Ursulin, Hannes Reinecke,
Jens Axboe, Bjorn Helgaas, Alexander Potapenko, Chen Fan,
Ingo Molnar, Peter Zijlstra (Intel),
Sebastian Andrzej Siewior, Johannes Thumshirn, Emese Revfy,
Sagi Grimberg, Eric Dumazet, Tom Herbert, Ben Hutchings
On Sun, 12 Feb 2017, Chris Wilson wrote:
> On Sun, Feb 12, 2017 at 03:46:09PM +0000, Chris Wilson wrote:
> > +void tasklet_enable(struct tasklet_struct *t)
> > +{
> > + if (!atomic_dec_and_test(&t->count))
> > + return;
> > +
> > + if (test_bit(TASKLET_STATE_SCHED, &t->state))
> > + raise_softirq(HI_SOFTIRQ | TASKLET_SOFTIRQ);
>
> And of course this can't work as raise_softirq() is local to the cpu.
Indeed. tasklets are a horror by design. We rather should make them go away.
Thanks,
tglx
^ permalink raw reply [flat|nested] 17+ messages in thread
end of thread, other threads:[~2017-02-17 11:56 UTC | newest]
Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-02-12 14:00 [PATCH] softirq: Prevent looping on disabled tasklets Chris Wilson
2017-02-12 14:00 ` Chris Wilson
2017-02-12 14:23 ` Chris Wilson
2017-02-12 14:23 ` Chris Wilson
2017-02-12 14:31 ` [PATCH v2] " Chris Wilson
2017-02-12 14:31 ` Chris Wilson
2017-02-12 14:32 ` ✗ Fi.CI.BAT: failure for " Patchwork
2017-02-12 15:04 ` [Intel-gfx] [PATCH] " kbuild test robot
2017-02-12 15:16 ` kbuild test robot
2017-02-12 15:16 ` kbuild test robot
2017-02-12 15:22 ` ✗ Fi.CI.BAT: failure for softirq: Prevent looping on disabled tasklets (rev2) Patchwork
2017-02-12 15:46 ` [PATCH v3] softirq: Prevent looping on disabled tasklets Chris Wilson
2017-02-12 15:46 ` Chris Wilson
2017-02-12 16:03 ` Chris Wilson
2017-02-12 16:03 ` Chris Wilson
2017-02-17 11:55 ` Thomas Gleixner
2017-02-12 16:22 ` ✓ Fi.CI.BAT: success for softirq: Prevent looping on disabled tasklets (rev3) Patchwork
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